Got a '70 Fastback Mustang with a 351 Windsor C4. Finally got it running consistant and strong with the exception of a squealing belt when I nail the throttle to wide open. I'm running one belt which runs the crank, fan and alternator. That's it. No accessories here. I've read that the pulleys can get "glazed" and that I should rough them up with a scotch brite pad or something. The fan pulley looks pretty shiny with the belt off. I can't get anymore tension on it since the tensioner has only one position when bolted in place. It is off an 89-93 5.0L

Do those tension pulleys lose their bite after time? Should I replace it with another belt too? It seems fairly snug when in place but for some reason that belt is slipping causing the squealing I guess. The only time it does it is when I drop the hammer. Very annoying and embarassing. Any help please? thanks.....dave